Sharif Digital Repository

Considering the importance of maintaining palm trees, this research focuses on the design of a climbing robot utilizing wheels. The goals of this robot include easy installation on the tree, climbing despite variations in trunk diameter and surface irregularities, maintaining static balance to prevent falling in a stationary state, and enabling tree pruning. Additionally, descending from the tree is an essential capability of this robot. For climbing, a rotating wheel and four auxiliary wheels are employed. A motor with a gearbox drives the rotating wheel, while the auxiliary wheels, supported by spring-lock mechanisms, provide the necessary force to prevent slipping and ensure stable... 

Researches on internationalization and export have categorized all factors as internal and external and most of them try to explain this behavior by studying external factors. Recent study in this field have shown that simply promoting specific behavior is not enough, and it is important to try to change the attitudes of managers toward internationalization. Utilizing Theory of Planned Behavior (TPB), this research tries to understand the relationship between attitudes of managers and internationalization behavior of an organization. the explicit objective of this research is to determine the factors which influence the organization behavior on internationalization (specifically indirect... 

In this thesis, study of some kinds of dual band transmission lines and structures are investigated. Attention to 3 important kinds, CRLH, SCRLH and the equal phase line are introduced and the formulations of each one are derived and considered. Also the method of designing these lines are attached. These lines form a complete category that makes the ability of designing all kind of dual band line with arbitrary frequencies and result phases with arbitrary non-integer ratio less or more than 1. Also an important attention is paid for the designing these lines in the microstrip configuration. Various kinds of Dual band structures are proposed at the last part of the introducing each lines.... 

Poorly damped Low Frequency electromechanical Oscillations (LFOs) confine the capability of power system transmission lines. This phenomenon, which is the result of dynamic interactions among generator groups, may make the system prone to small- signal instability in some cases. Due to the use of some system controllers such as AVRs, these oscillations are inevitable.
Hence, electromechanical modes detection and assessing stability margin are important requirement in power system planning and operation, and can provide significant help to power system operators by preventing stability problems.
From the distant past, in order to monitor small-signal stability, power system operators... 

Nowadays in Iran service providers, are using copper lines in access networks. They rent these lines from a governmental telecommunication company during a complicated and time consuming process. In this thesis, the most common access technologies have been analyzed in order to find an alternative solution for copper lines. Based on the studies in this thesis, it is clear that Wimax technology can be an appropriate solution comparing with Wi-Fi and 3G from the point of quality and speed. The UNIDO methodology has been used in this economical assessment (feasibility study). In this methodology, all the running and fixed costs and revenue as well, have been estimated. In the next step,... 

The recent breakthroughs in the lab-on-a-chip technology will not be directly used as clinical devices unless the specific applications are carefully tested and certified. As there is a growing trend towards microfluidic devices for biomedical research, an active microfluidic device was developed. Common microfabrication methods were used to develop a microchip to separate and concentrate live and dead cells based on the dielectrophoresis phenomenon. Unique capabilities of the dielectrophoresis phenomenon make it a powerful tool for micro particle manipulation in micro scale. In this research, geometry for the mentioned purpose is designed and optimized. Three-dimensional microelectrodes are... 

The aim of this study is to design a control system for an autonomous underwater vehicle and evaluate this system for different missions. Due to the non-linear behavior of the target robot, both linear and non-linear behavior of the system was studied. Model Predictive control method has been implemented since it can outline both linear and non-linear controllers. The first non-linear dynamics of this robot, maneuvering equipment, and external disturbances (waves and ocean current) were modeled. Then, to design the linear controller, the equations of motion have been linearized around the working point(cruise speed). In order to analyze both designed controllers, various duties have been... 

In this piece of work, a gravity model is suggested as Iranian non-fuel export model to OIC countries. The most important results out of this model are the acquired coefficients of two variables, namely “ECO membership” and “Economic and Trade Freedom of Importer”. At first, we expected that for importer, being a member of ECO would increase the amount of trade with iran. Surprisingly, this is not what we see in a model. In fact, as ECO has not achieved any tangible success in increasing trade between its members, eastern Asian Muslim countries has become an important trade partner for iranians. This result is compatible with other pieces of researches about ECO. “Economic and Trade Freedom... 

Today’s growing interest to the underwater explorations and navigations demands to design appropriate underwater communication methods and systems. However, radio frequencies which are widely being used in free space communications, can’t be a good candidate for underwater wireless communications, due to their sever attenuation in water. On the other hand, underwater acoustic communication has been widely studied and implemented in the past decades, inspired by suitable propagation of acoustic waves through the underwater medium. Nevertheless, acoustic communication systems have limited bandwidth, lower propagation speed and lower security than optical counterparts, which suggests underwater... 

Visible light communication (VLC) uses huge license-free spectral bandwidth of visible light for high-speed wireless communication. Since each VLC access point covers a small area, handovers of mobile users are inevitable. In order to deal with these handovers, developing fast and effective resource allocation algorithms is a challenge. this paper introduces the problem of mobility-aware optimization of resources in hybrid VLC and 5G radio access technologies networks using the T-step look-ahead policy and employing the notion of handover efficiency. It is shown that the handover efficiency can correlate the overall performance of the network with future actions based on the mobility of... 

In present research, a cohesive based finite element model has been introduced to estimate median crack depth during mechanical machining on optical glasses. Development of the machining numerical model has been initiated by investigating the indentation process. Experimental results of this step have been calibrated primary numerical model which has been used in the scratch process. Due to differences between the scratch mechanism and indentation one, mathematical bases fracture formulas and cohesive relations have been developed. After extracting primary result, using them in the scratch model and developing the primary model, ultimately numerical model has been evolved to an abstract... 

Many embedded processors are used in harsh environments and their behavior should be investigated against the incidence of common faults. Fault Injection is a prevalent method to do this investigation. Simulation-based fault injection is one of the most prominent forms of fault injection. A fault model is required to do simulation-based fault injection. Simulated faults should have the most similarity to the real faults. Temperature variation and in the extreme case thermal shock is one of the probable faults in harsh environment. In this thesis, we want to propose fault models for thermal shock in various abstraction levels, evaluate and compare these fault models and present methods to use... 

Hydrothermal supercritical method is one of the most suitable methods for metal oxide nano powder, ceramics and mineral catalyst synthesis. Metal oxides nanopowder in its pure or mixed form has wide potential application as chemical industrial catalyst, hot Superconductors, magnetic material, gas sensors and car catalyst convertors. One of the most important metal oxides aspects of application is uranium oxide as nuclear reactor fuel is used. In addition, UO2 is selective catalyst for converting methane to methanol process and Decomposition of organic Chlorine material. In Supercritical hydrothermal method done in high pressure reactor with critical to fluid, is new method for the... 

Lithium has 9 isotopes which two isotopes are stable and remaining isotopes are unstable and have half-life. Lithium stable isotopes include 6Li and 7Li that their abundance is 7.53% and 92.47% respectively. Importance of lighter lithium isotope appears for its small cross section against thermal neutron and producing fusion reactors fuel in nuclear industries. Thermal neutron absorption cross section for 6Li and 7Li are 950 barn and 37 mbarn respectively. Interesting of these isotopes in nuclear industry is due to the large difference in the absorption cross section.6Li compounds implied for tritium producing in coat of nuclear fusion reactor with DT fuel. Following tritium is used in... 

Foil gas bearings are compliant surface, self-acting hydrodynamic bearings that use ambient gas as their working fluid. They do not require external pressurization and are typically constructed from several layers of sheet metal foils. In high-speed, high-temperature applications the GFB’s have the advantage of developing higher load capacities than with fixed geometry gas bearings. Since GFB’s have a complex structure consisting of a spring-like substructure with an overlying flexible surface, there exists a great variety of permutations on any given design. At current work presents a 1D model for GFB with couple solving Reynolds and Euler-Bernoulli beam equation. This mean top foil assume to... 

Lameness in dairy cattle is a crucial welfare issue in dairy industry, and over the years scientists are attempting to present a detection method. In recent years it is attracting more attention to make the identification and discrimination of sounds and lames systematic and automatic. Right now, the most hopeful results have been obtained through the measurement of Ground Reaction Forces (GRF) of hooves, and analysis of load distribution between four legs, which seems applicable for wide use in dairy industry. However, the accuracy, validity, and reliability of discrimination is still far from an acceptable point, that is because of a great lack in understanding quantitative effects of the... 

Natural boron consists of two stable isotopes, mass 10 (19.3%) and mass 11 (80.7%). 10B isotope has a large thermal neutron capture cross-section and it therefore, used widely in such aspects as modern industry, military equipment, medical science and so on. specially the demand of atomic energy industry for the boron isotope is increased severely. So the separation of 10B from natural boron has received very wide attention at present. There are many kinds of methods on the boron isotopes separation, such as chemical exchange reaction and distillation in boron trifluoride method, ion exchange in boric acid solution method, counter current recycle membrane cascades in boron trifluoride... 

In this study the feasibility of xenon separation from xenon-krypton mixture was investigated by utilizing of the chromatographic column filled with nano and micron sized NaY zeolite. For this purpose the nano NaY with the yield of 100% related to Al2O3 and the average size of 98.6 nm was synthesized through the clear solution method with the mid-adding of NaOH. Furthermore, a novel method for granulation of nano zeolite was developed by utilizing sodium alginate as an external template. In this method the production of uniform spherical granules with the different sizes in the range of several milimiteres to 100 µm was easily performed. Moreover, the results showed that the adding of... 

Natural boron includes two stable isotopes 10B and 11B with 19.3 and 80.7 weight percent respectivley.10B isotope has a high thermal neutron absorption cross section. So isotope 10B material is suitable for making atomic reactor control rods. Other and even more important applications of 10B are in disclosing neutrons in order to measure neutron reactors fluxes and also are in nuclear physics laboratories and medical radiation. This isotope also is used in the pharmaceutical and the military industries. There are several methods for separating boron isotopes. Among the distillation methods, thermal diffusion of BF3, distillation of BF3, distillation of methyl borate, boric acid distillation... 

Due to both dynamic and opportunistic spectrum access, Cognitive radio networks is a promising solution for spectrum scarcity problem. In cognitive radio networks, users need to have a control channels in order to cooperate for sharing the sensing information, channel sharing and etc. In Ad-hoc cognitive radio networks because of the absence of infrastructure and central nodes, every user runs a distributed algorithm to create a common control channel. If the control channel gets jammed, network’s performance degrades dramatically, therefore the jammer’s target in cognitive radio networks is the control channels to disturb the networks’ performance. The traditional solution to confront...